Black-vented Shearwater

Puffinus opisthomelas

Most shearwaters range widely over the ocean far from land, and most of those seen off our Pacific Coast nest only in the southern hemisphere. The Black-vented Shearwater is an exception, nesting on islands off northwestern Mexico, traveling only short distances north along the California coast, and usually staying within a few miles of shore. Observers at coastal lookouts may see this bird in late fall, flying with rapid wingbeats and short glides low over the waves.

Conservation status

Numbers appear to be stable, but vulnerable to introduced cats and other predators on nesting islands.

Open ocean near coast. Found closer to shore than most shearwaters, over continental shelf within a few miles of the coast. Favors warm waters at all seasons: fewer move north along California coast in years when sea surface temperature is lower. Nests on islands with enough soil for burrowing or with natural crevices in rock.

Most shearwaters range widely over the ocean far from land, and most of those seen off our Pacific Coast nest only in the southern hemisphere. The Black-vented Shearwater is an exception, nesting on islands off northwestern Mexico, traveling only short distances north along the California coast, and usually staying within a few miles of shore. Observers at coastal lookouts may see this bird in late fall, flying with rapid wingbeats and short glides low over the waves.

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Feeding Behavior

Forages by seizing items at or just below surface while swimming, by plunging into water from low flight, or by making shallow dives from surface. Apparently does not dive as often nor swim as well underwater as the similar Manx Shearwater.

Eggs

One. Dull white. Incubation probably by both sexes, as in other shearwaters; incubation period not well known. Young: Both parents probably feed young, by regurgitation. Development of young and age at first flight not well known, but young probably remains in nest at least 2 months.

Young

Both parents probably feed young, by regurgitation. Development of young and age at first flight not well known, but young probably remains in nest at least 2 months.

Diet

Probably mostly fish. Diet not well known. Off southern California may eat mostly small fish, including herring and sardines. May also eat small squid, crustaceans.

Nesting

Breeding behavior not well known. Nests in colonies on islands. Active around colonies only at night. Both members of pair may rest in nest burrow during daytime before egg-laying. Nest: Site is in burrow in ground, sometimes in crevice in rock. Burrow may be more than 10' long, often with turns to the side rather than straight; probably both sexes help dig burrow, as in related species. Nest chamber at end of burrow may have a few bits of plant material or may be unlined.

Migration

Moves north from Baja into California's coastal waters in fall. Numbers and timing variable: when sea temperature is high, may arrive early and in large numbers. Some also may move well to south of breeding range, but southward migration poorly known.

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Migration

Moves north from Baja into California's coastal waters in fall. Numbers and timing variable: when sea temperature is high, may arrive early and in large numbers. Some also may move well to south of breeding range, but southward migration poorly known.